Controlling the fuel delivery to an engine is a recognized technique to affect the traditional operating characteristics of the engine, such as engine speed and torque. More recently, it is one of several ways used to reduce the emissions, such as NOx and particulates from the engine.
When the engine is operating at idle speeds, or light or no load conditions, conventionally a relatively small amount of fuel is delivered, e.g., injected, into each combustion chamber of the engine by a fuel delivery device, such as a fuel injector.
As a practical matter, however, each fuel injector has a minimum controllable amount of fuel that it injects each time it is activated. This is typically due to inherent constraints and tolerances in the design and manufacture of fuel injectors. Thus, if a desired amount of fuel to be injected is less than the minimum controllable fuel injection quantity, either no fuel may be injected, or the minimum quantity may be injected, or some quantity in-between. In any case, a quantity of fuel that is different from what is desired may be delivered to the combustion chamber of the engine. This can lead to undesired emissions or engine performance.
With the advent of multi-shot injections, e.g., more than 1 shot of fuel per cylinder per combustion cycle (intake, compression, power, and exhaust for a four stroke engine) the quantity of fuel delivered per combustion cycle is divided into two or more injections. Thus, the quantity of fuel per injection is smaller, and the fuel injector is more likely to run into the problem described above.
SUMMARY OF THE INVENTION
The present invention provides apparatuses and methods for delivering fuel to at least two combustion chambers of an engine. A fuel controller receives a first fuel quantity signal indicative of a first desired quantity of fuel to be delivered to each combustion chamber of the engine during a combustion cycle. The fuel controller transmits at least one second fuel quantity signal as a function of the first fuel quantity signal, and transmits at least one third fuel quantity signal as a function of the first fuel quantity signal. The second and third fuel quantity signals are indicative of a respective second and third desired quantities of fuel to be delivered during a combustion cycle. The sum of the fuel quantities corresponding to the second fuel quantity signals transmitted during a combustion cycle are less than the first desired fuel quantity.